Fuel and process for burning same



Patente Mar. 6, i923.

ROBERT A. LIPSCOMB, CF HOLT, ALABAMA.

EUEL AND PROCESS FOB BURNING SAME.

Application filed June 27, 1921.

residing at Holt, in the county of Tusca loosa and State of Alabama, have invented certain new and useful lmprovements in lTuel and Processes for Burning Same, of

which the following is a specification.

This invention relates to a novel type of fuel and an improved process for the most eliicient burning of the same.

My invention contemplates the production of an improved type of fuel especially adapted to maintain an elongated and substan tially uniformly heated zone of heat interception, which for boilers will be relatively short compared to nodulizing and cement kilns which require, for ideal operation, a very long zone of heat interception which will be free from zones of heat sufciently intense to cause fusion.

My invention contemplates the production of a fuel capable of producing the above results by the combination of fuel particles, part of which are of such quick burning character as to be readily consumed toproduce the requisite initial zone of heat interception in passing through which the other slower burning particles will become ignited and as they burn will extend the zone of heat interception to the desired length. rlhe twodifferent grades of particles may be obtained either by the selection of fuels having diffen ent percentages of volatile matter or by the combinations of different sized particles of the same or similar fuel. Obviously, where the fuel is composed of particles carefully selected as to size, as for instance, a definite percentage of finely ground fuel mixed with adeinite percentage of much coarser particles of the same fuel, the latter will take longer to be consumed, and as my invention contemplates introducing the fuel aggregate by means of an air blast so that the particles are carried on an air or gas current while being consumed, it follows that the slower burning particles will extend the length of the zone of heat interception and increase the uniformity of its temperature, it being noted that the reduction in the percentage of the total fuel consumed near its entrance Serial No. 480,884.

vin the combustion chamber will tend to reduce the objectionably high temperatures which tend to exist there.

My invention further contemplates the selection of a. high carbon fuel such as is available in ideal form in coke breeze at present generally considered a waste product, and the combining with this of a relatively lower carbon fuel having a high percentage of volatile matter such as waste culm from bituminous coal washings, crushed bituminous coal, or, under certain conditions, gas.

My invention contemplates the reducing of these fuel elements to a finely pulverized condition and their mixture in such relative proportions as to give to the result-ant fuel aggregate a sufficient percentage of quickly burning highly volatile fuel to sustain the character of combustion in the initial combust-ion zone necessary to produce the requisite temperatures for the ignitionand the ultimate complete consumption of the slow burning high carbon or coke element of the fuel. ln utilizing a fuel of this character so as to produce the maximum heating etliciency therefrom, my invention contemplates the discharge of the pulverized aggregate by air blast into a combustion chamber which may take the form of a boiler furnace, aV cement kiln, or a lriln for nodulizing metallic products. In all of these uses the highest heating efliciency will be obtained if the temperature produced by the combustion of the fuel can be sustained within approximate control and with substantial uniformity throughout a long zone of combustion, as by this means the objections to a restricted extremely heated zone, are avoided as well as the many physical disadvantages resultingfrom localized intense heat which it has not heretofore been possible to overcome.

' My invention is based on the theory that the ideal fuel will be obtained when one is found that is capable of sustaining a moderately intense heat throughout an entremely elongated zone, and this is obtained by my proposed fuel in the manner which will now be described.

Assuming, for the salie of illustrationA` that my improved fuel as last above described is to be burned in a nodulizing kiln where ideal combustion conditions would carbon fuel would burn if. ignited; at this point. i The combustion of .this 'parto-f the fuel aggregate takesV4 place in a shortinitial1 combustion zone, in which thehighly v ola tile fuelselements will produce a sufficient temperature, asthe high carbon fuel particles., are carried along'y through it, to cause their ignition and subsequent gradualcombustion'V as they traverse the combustion chamber.. Ther desired results flow` from `this methodof combustion4 of the fuel` because the; initial combustion Of` theV lowI carben` high volatile fuel will be uick and of relatively low7 temperature w ile the coinbisti'on 1f-the high carbonnori-veletle, fuel will be slower and at a relatively higher temperature matelyconsumed at theendwof a travel, the lengthofwhich is determined bythe draft conditions in the kiln, the size of the-particles,the desired operating temperatures in. the;kiln, andthe regulationof the admission ofoxygen.y These four factors: determine the length of thezone of active combustion of. high carbon fuel-obtained and the temperature thereinas follows. If the relative proportions ofthe low carbon fuel compo nentto the high carbon fuel componentbe increased the aggregate length of thezone of active `combustion will be decreasedin proortionto the decrease in the percentage of carbon in the aggregate; by decreasing the relative percentage of the low carbon fuel component" within the limits which will enableit toignite the highcarbon fuel, the

length of the zone of active combustion will beincreased; by increasing or diminishingv the volume of air admitted I can accelerate orretard the rate of combustion of the high carbon fuel coniponentand thus control the lengthof the combustion zone; and byregulating the draft, the rate of travel ofthe burning fuel particles can be controlled and thev length of the combustion zone regulated.

A fuel aggregate composed of the pulver-Y ized and larger sized particles in suitable proportions can be used to produce the initialland extended Zones of combustion just as aboveV described and by varying the relative proportions of large to small particles which. will beA isustained thipiiglioutv a long zone of travel of the highl 'carbon fuel particles which will beultithe length of the heat interception zone can be regulated.

' It will be obvious that the mobility of my improved fuel during its combustion is Van importantand essential factor in my combustion process because by this means l' am enabled to take advantage of the movement of the burning fuel particles so as to extend the zone of active combustion and it is in this respect that my invention distinguishes most clearly from the combustion of pre` vious fuel.y mixtllr in which coke and varions grades of vcoal have been combined but in which they were burned infixedlocation,

Myj invention also Vdistinguishes `inlirnportant respects fromA thepractice heretofore obtaining4 of burning pulverized localiv whether anthracite or bituminous, or. amiXf ture of the two, under boilers, because inall such fuels all particleshave` possessed the volatile inattertoa high degree as compared with coke and it has 4not been discovered Vthat byy their sizing. or. uselselectively the lengtlieningof the 'zonev of active combustion and ,the maintenance. 'of` a `substantially uniform temperature throughout saidfz'one, was

possible.V It., is important,- in obtaining the results which l contemplate, that the high carbn fuel, shall haveno appreciable volal tile matter and especially that hydrogen. and combined moisture should not bejpresent in appreciable quantities as these' either counteract or disturb the effects desired. It is the absence in appreciablev degree orfvola tile matter, combined moistureand hydrogen inthe coke whichenables the most practical control and regulation robe obtained,as the action ofV the' carbon particles underA the known conditions inthe combustion zone can be very accurately determined, but this is not possiblezwhere thehighcarbon fuel carries appreciable percentages of volatile matter, hydrogen and combined moisture.

My invention is` of especial importance as a fuel forfuse in, and as a method of fir,- ing, kilns, and particularly,nodulizing kilns, where idealconditions obtain when the coinbustion zone can be extended as-farj as possiblethrough the kiln and excessive temper` atures of fusion zones avoided at the dis-V charge-end, as such excessive temperatures in a concentrated zone tendsboth to glaze the nodules and to reduce the quantity and quality of the product. l

hly invention therefore in its preferred' form consists in mixing coke or coke breeze with coal or culin from coal washers pulverized toa degree of neness thatwillfbe requiredby the` rate of combustion desired,- and in such proportions as will develop the most economical calorific intensity for the use contemplated.

The -calorific intensity of my improved fuel depends not only on the quantity of heat evolved, but also on the rate ofzcombustion,

and the capacity of the products of combustion to absorb the heat. For example, the oxidation of wood during slow decay releases the same number of heat units as if the wood were cast into a fire and burned, but the calorific intensity attained in the two cases is very different.` rlhe caloriic intensityy maybe calculated it' the above factors are known, or it may be measured directly by thermometers, pyrometers, or any device which is aifected by changes of temperatures.

The caloriic intensity of a given fuel is the ratio between its power to develop heat and the power of the resulting products of combustion to absorb the Vheat produced. For example, the caloric intensity ot carbon when burned in an atmosphere of oxygen alone is found to be 6,388 degrees F. When, however, the combustion off carbon takes place in oxygen of the air with its accompanying nitrogen, the products of combustion are increased by just that quantity of nitrogen, which, in turn, absorbs its share of heat developed and the resulting temperature is correspondingly low or 3,127 degrees F. Thesot coals contain from 50 to 75 percent of carbon and from 20 to 40 percent of combustible gases. These gases also Vcontain a large percentage of carbon combined with hydrogen, and are generally known as hydro-carbon gases. Carbon has a strong ailinity for oxygen at elevated temperatures, and when burned in the presence of air or tree oxygen it is capable of torming two oxides, CO, known as carbon monoxide, andC()2 known as carbon dioxide, or carbon anhydride. Both CU and C02 are l fixed gases, transparent and invisible, but

they differ radically in character. C0 is an unsaturated compound capable of taking up another atom of oxygen and forming CO2. ln other words, it is combustible. It burns with a blue iame which is familiar to us in hard coal or coke res, giving very little light but much heat. CO2 on the other hand, is a completely saturated compound and can take up no further additions of oxygen. It is therefore incombustible. It is a heavy gas, being about one and one-half times as heavy as air. The coke or coke breeze used has a maximum of CO2 and a minimum of CO, hence its substitution for coal.

The theoretical temperature ot the combustion of carbon to the condition of CO in the presence of air is 2270 degrees F. The theoretical temperature of CO burned in air is somewhat higher than that accompanying its formation or 3080 degrees F. It is there tore evident that the calorilic intensity of and the temperatures therein can be controlled, and, in rotary kilns for nodulizing iron bearing materials, the ability to control the zone oi' incipient fusion shows the following advantages, to-witz Increased production.

Control of ring in kiln.

Less fuel per ton of product.

Easy control of temperatures.

Increased porosity.

Reduction of fines.

Increased production is due to uniform temperatures through a much longer area oit the kiln than is possible when coal only is used. The zone of incipient fusion where coal is used is not more than 2O to 25 feet. whereas, when an equal mixture of coal and coke breeze that will pass a 35 mesh screen' is used, it is from 50 to 60 feet. The long zone of critical temperature necessarily subjects the material to longer treatment at this temperature, which in turn accounts for the absence of thetranslucent and glass-like structure of the iron silicate enveloping the oxide of iron, usually noticed when contracted zones of very high temperature are used. The same application of critical temperature will obtain in cement kilns with equally advantageous results.

The absence of ring formation in kilns is due to the excess amount of carbon and lower volatile and combustible matter in my improved fuel as compared with coal. The high carbon and low volatile matter naturally requires more air and longer time to complete combustion' than does the coal which explains the longer zone of incipient heat interception, and the absence, to a marked degree, of the contracted zone of heat interception of a temperature sufficiently high to cause fusion.

Lower fuel cost and easy control ot' temperature is due primarily to the use of coke or coke. breeze, as cokebreeze is considered waste product, and the cost may be 'further reduced by the use ot culm, or washer waste from coal washers, as ya low carbon mix with the coke breeze.

My invention contemplates the use of a mixture of high carbon material with low carbon, high volatile and combustible martE ter, the same being pulverized to a condition of very minute particles. This finely divided material. to lbe burned in a current of mixture of air. Any of the devices designed to handle pulverized coal will handle this pulverized fuel which is available for use in any and all metallurgical devices for heat treatment, cement kilns, steam boilers, brick kilns, pctteries, glass furnaces or any heating or fuel fed device wherein any carbonaceous material can be used to generate heat.

In the illustrative drawings of a typical apparatus for firing `a nodulizing kiln.

llO

Eig ll isa viert: in velevation ofthe. fuel birrfand fuel delivery.l mechanism with the,

delivers-.it intoan air-blast pipe by which .it-'is blownl With-a lblastofl air through the The nozzle enters` nozzle 6-.-intothelriln 7. the kiln. through the end fdofor 8 which affords control: of the volume of air ad'- mittedr vrPhe low carbon volatile constituent offtheduel is burned in thefincipient com-i bustion; zone indicated` typically in Figay 2, Whereasthe highcarbon fuel, ignited-inthe incipient combustion zone is consumed throughout the greatly extended alone in dioatedzy WhenlE refer to an air current l intend tof include any oxygen` bearing currenty of gas byl'whieh the burning particles offuelare carried and which supplies to theinthe needed; oxygen for their sustained combus tion.. i

Havingthus described my invention, Whatl `claimas new andfdesiretor'secure by Let tere Patent, is z- 1. The hereindescribed process for priof ducing-an elongated and substantially uniformly,l heated zone of heat interception, which consists in blowing into a combustion chamber finely divided particlestof colreain combination With suiiioient lvolatile combustible matter toproduceby its combustion an initial ltemperature Which-Will ignite the particles ofcole.

2 1The hereindes'cribed process for producing an elongated and substantially uniformly heated zone ol heat interception, which consistsiin blowinginto a combustion chamber finely divided particles of highly carbonaceous material substantially free oi volatile matter, hydrogen and combined moisture incombination with sulicient volatile combustible matter to produce by its combustion an initial temperature which.

will ignite the particles ot said carbona ceousmaterial, and regulating the zone of combustion of the carbonaceous material by control of the volume of oxygen admitted.

3. The hereindescribed process for producing an elongated and substantially uniforinly heated zone of heat interception, which consists in blowing into a combustion chamber finely divided particles of coke inl combination With suliicient volatile com- 2,'is a diagrammatic view indicating' Volumt'Of-Oxrgen admit d. 'i

4. The, hereindescribedfprocess for pro and regulatingvthh lgtli: ofthej zone oi* e combustionpf. the eolie. artieles by',contro lg` of the :volume of ,oxygen admitted andthev relative. .peroeiita'gefl ofcolte-.tn

5- Yv'lhfevl1@Feindeserbed' process fjorj pro'- dueing. an elongated fand substantially 'unil forinl'y 'heatedfzone of heat 'interee tion,

which consistsfin blot/vying .into a cpinbu ion` i combustible matter' andsxyeite" predilie'" by itscombustion an initial temperature which Win4 ignite the pau-,ities retreats-4 they pass' theifthrloush`jaid fellletat. th zone of Qombustionjofjth. Y".'c,ol` e"by"xfmti'olr of the volume. of, oxygen admitted, bythe relative. percent-'age of" coke" to` combustible" matter,u in the'y fuel aggregate, arid by 'the4 regulation of thevelocity o ftli'oyv vof the Vfuel particles i responsive to the idraftf condition in the combustion chamber.'V

6. The hereindescribedl"process .ofV producing an elongated' and substantially unie' formly heated- 'zone' ',oi" heat" interception; which consists in discharging a miirtureiof-V pulverized coke 11d Coalby means o f'an air blast into a combustion chamber, regulating theadmission of oxygen' tothe chainber, and restricting the volume' of coalto that requisite to ignite the particles ocoke in the initial combustion' zone,` leaving Athe latter tocompletetheir combustion asthey traverse the combustion chamber. Y

7. The hereindescribed"method of firing kilns, which consists in providing a pulverized fuelfaggregate composed ot'colreI and coal, restricting the relative percentage oir'y coal tothat necessary to produce a predetermined temperature in the initial combustion zone, and controlling the rate of 4'combustion ofthe particles of coke ignited. inthe initial combustion zone by a regulat-ion otthe volume of oxygen admitted' to the kiln,

8. The hereind'escribed method of firing kilns, which consists in providing a pulverized fuel aggregate composedA of coke and coal, restricting the relative percentage of coal to that necessary to produce a predetermined temperature inthe initial combustion zone, and controlling the rate of combustion of the particles of coke ignited in the initial combustion zone by a regulation incipient fusion having a predetermined temperature, and to extend said zone of incipient fusion by the combustion of the particles of high carbon material ignited in said initial Zone, and controlling the length of heat of said extended zone by a regulation of the volume of oxygen admitted and the rate of travel of the burning high carbon particles.

In testimony whereof I aiiiX my signature.

ROBERT A. LIPSCOMB. Witness:

Norm: WELSH. 

